1. Field of the Invention
This invention relates to well tools, and more particularly to gripper units for use in injectors for coiled or reeled tubing, or similar elongate objects.
2. Related Art and Information
Reeled or coil tubing has been run into wells for many years for performing certain downhole operations such as, for instance, washing out sand bridges, circulating treating fluids, setting downhole tools, cleaning the internal walls of well pipes, conducting producing fluids or lift gas, and a number of other similar remedial or production operations. In addition, such injectors have been found useful in performing operations in horizontal and slanted wells.
Use of such reeled or coil tubing saves much time and money because the reeled tubing injectors force the reeled tubing into the well through a seal such as a stripper head, and may do so continuously and at a good rate of speed. Since the tubing is in one piece, time is not lost in having to make up a threaded connection about every 20 to 30 feet (6.1 to 9.14 meters) such as when jointed pipe is used. Further, such injectors can be moved to be jobsite, set up, and moved off the job much quicker and less costly than can drilling rigs or workover rigs.
Many such reeled tubing injectors are in common use today and a number of patents relating thereto have been issued. Typically, most of the reeled tubing injectors utilize a pair of opposed endless drive chains which are arranged in a common plane. Such drive chains are made up of links, rollers and gripper blocks. In some cases gripper inserts are used. These drive chains are generally driven by sprockets powered by a motor, such as a reversible hydraulic motor. The opposed drive chains grip the reeled tubing between them. These drive chains are backed up so that a goodly number of pairs of opposed gripping blocks are in gripping engagement with the tubing at any given moment. As the chains are in motion and the tubing is being driven, each time a pair of gripper blocks is actuated to release their hold on the tubing another pair is actuated to gripping position. The moving drive chains are thus able to force the tubing into the well, or to remove the same therefrom depending upon the direction in which they are driven.
A number of patents have been issued relating to reeled or coil tubing injectors. Among those are the following U.S. Pat. Nos.:
2,679,924 3,258,110 3,285,485 3,559,905 PA1 3,754,474 4,515,220 4,655,291
U.S. Pat. No. 2,679,924 which issued to P. R. Powell on June 1, 1954 for "STRAND-ADVANCING APPARATUS" discloses an apparatus employing a pair of opposed drive chains each having a multiplicity gripping shoes for gripping and moving a strand, cable, or the like, as the chains are driven. The gripper shoe 20 is shown in FIG. 5 to have a concave groove for engaging and gripping the cable, or the like, being moved. This groove has a radius slightly larger than the radius of the largest object to be moved. (Col. 2).
U.S. Pat. No. 3,258,110 issued to D. W. Pilcher on June 28, 1966 for "ENDLESS CHAIN APPARATUS". This patent discloses opposed drive chains having gripping elements 15 with concave gripping surfaces. (Col. 2 and FIG. 2).
U.S. Pat. No. 3,285,485 issued to D. T. Slator on Nov. 15, 1966 for "APPARATUS FOR HANDLING TUBING OR OTHER ELONGATE OBJECTS". This patent discloses drive chains including gripper units (FIG. 6-7) which are connectable one to another by the pins 15 which also pass through the chain links 11a and rollers 11b. (Col. 3, line 10 et seq.). This U.S. Pat. No. 3,285,485 is hereby incorporated herein for all purposes.
U.S. Pat. No. 3,559,905 issued on Feb. 2, 1971, to Alexander Palynchuk for "METHOD AND APPARATUS FOR RUNNING AND PULLING A CONTINUOUS METAL MEMBER INTO AND OUT OF A WELL". This patent discloses a track assembly 2 including opposed sprocket chains 10 each having gripping pads 11. (Col. 4, lines 42, et seq.) (FIGS. 10-12). Elements 41 which frictionally grip the rod 4 "will preferably be made of somewhat flexible material in order that it may be used with rod strings of varying diameters. An element formed of urethane elastomer having a Shore durometer range of D-50 has been shown to be suitable." (Col. 5, lines 32-39).
U.S. Pat. No. 3,754,474 issued to Alexander Palynchuk on Aug. 28, 1973 for "GRIPPER PAD". This patent discloses a gripper unit for use in an apparatus such as that disclosed in U.S. Pat. No. 3,559,905, just mentioned. This gripper unit includes "a gripper pad 3 which includes a block 4 having studs 5 embedded therein. (Col. 2, lines 33-34). Block 4 is of a deformable elastomer material (line 43) and studs 5 are "of a metal softer than steel, preferably aluminum or aluminum alloy." (Col. 3, lines 6-16). U.S. Pat. No. 3,754,474 is incorporated into this application by reference for all purposes.
U.S. Pat. No. 4,515,220 issued on May 7, 1985 to Phillip S. Sizer, Don C. Cox, and Malcolm N. Council for "APPARATUS AND METHOD FOR ROTATING COIL TUBING IN A WELL". This patent discloses a reeled or coil tubing injector which can handle coil tubing and also handle jointed pipe on the upper end thereof, even rotate it in a well. While the gripping blocks on the chains will grip both the coil tubing and the quill through which the pipe is run, the grippers grip only one size. Their gripping surfaces are concave or semi-circular in section. The quill is provided with ridges which are the same radius as the coil tubing. (See in FIG. 17 coil tubing 50 and in FIG. 20 the quill 75). This U.S. Pat. No. 4,515,220 is incorporated herein by reference for all purposes.
U.S. Pat. No. 4,655,291 issued to Don C. Cox on Apr. 7, 1987 for "INJECTOR FOR COUPLED PIPE". The disclosed apparatus utilizes the same type of drive chains and gripper blocks as does the apparatus of U.S. Pat. No. 4,515,220 just mentioned. This U.S. Pat. No. 4,655,291 is incorporated herein by reference for all purposes.
Publication "DEEP EARTH SAMPLING SYSTEM-PHASE I", Final Report of National Science Foundation, dated June 1990 and published by MAURER ENGINEERING INC., Houston, Tex., discloses various concepts for handling tapered strings of coil tubing. These concepts are: use of stacked injectors, each adapted for a different size of tubing (page 20); an injector having two independent mechanisms to handle two sizes of tubing (page 21); gripper units having three sizes of gripper grooves side by side for handling three sizes of tubing. The drive chains of this apparatus would need to be shifted laterally for each diameter change (page 21); and gripper blocks for accommodating two sizes of tubing through providing gripper blocks for small tubing with a second, larger radius to fit a larger diameter tubing (page 26).
None of the prior art of which applicant is aware teaches or suggests gripper blocks for reeled or coil tubing which will provide an adequate grip with less squeeze and which will grip tubing or similar objects of various sizes.
Grippers for reeled or coil tubing generally have been formed either from an elastomeric material which would conform to the shape of the tubing exterior and take a friction grip thereof, or formed of steel and provided with notches having a radius slightly greater than that of the tubing. These steel grippers took a vise-like grip on the tubing and although they fit the tubing fairly closely, excessive squeeze often resulted in the tubing being distorted to an out-of-round condition and scarred. The problem was that the squeeze was applied to the tubing at two points opposite each other at 180 degrees apart. Early failure of the tubing and the stripper seals is understandable.
Such grippers are used extensively today, and since it is known that they can distort and scar the tubing, and since longer strings of tubing are needful in the industry, it has been desirable to provide improved grippers for reeled tubing which will overcome the shortcomings of the existing grippers, and at the same time readily grip tubings of various diameters. The present invention is an improvement over the gripping blocks used in the known prior art and overcomes many of the shortcomings associated therewith, and are more suitable for use in the modern oil industry where wells are deeper, conditions more severe, operations more costly, and damaged or ruined reeled tubing can cause considerable delays and added costs.